CALCIFIED RENAL MASSES

JOHN PATTERSON, M.D. G. BRISCOE D. LOHR ROBERT C. FLANIGAN, M.D. C. BRISCOE

From the Department of Surgery, Division of Urology, University of Kentucky Medical Center, and the Veterans Administration Medical Center, Lexington, Kentucky

ABSTRACT-A review of the literature and the University of Kentucky Medical Center/Lexington Veterans Administration Medical Center experience regarding caltification of renal masses was undertaken. Twenty per cent of calcified renal masses .cannot be easily characterized by CT scan as malignant or benign and are indeterminate. These lesions must be followed closely with follow-up CT scanning or undergo surgical exploration, a-s 40 per cent may be malignant.

The significance of calcification in renal masses has been a subject of controversy since the turn of the century, when Albrechtl described a re- nal cell carcinoma surrounded by a calcific cap- sule. Braasch and Griffen in 1936e reported that 7 of 283 renal cell cancers were calcified and that 4 of these 7 patients were alive at five years. They concluded that calcification there- fore constituted a favorable prognosis. Cahill and Melicow in 1938,3 came to the opposite conclusion finding 12 of 82 renal cell cancers calcified, but only 1 of 12 patients surviving two years without demonstrable metastasis.

Prior to the advent of computerized tomogra- phy (CT) scanning, radiographic evaluation of several large series of renal masses revealed calqification in 4 to 11 per cent.4s5 Calcification has been reported in a wide variety of situa- tionqe15 most commonly renal cell cancer, but also less commonly in cystic renal disease, infec- tious processes such as abscesses, echinococcal cysts, schistosomiasis, tuberculosis, and xantho- granulomatous pyelonephritis, and vascular etiologies such as arteriovenous fist&s, aneu- rysm formation, angiomatous malformation, and hematoma. Other malignancies, such as Wilms tumor and neuroblastoma, are calci- fied, 8 per cent and 55 per cent of cases, respec- tively. Osteo- and chondrosarcomas and transi- tional cell carcinomas also have been reported with radiographic calcification.5,16

UROLOGY I APRIL 1987 I VOLUME XXIX. NUMBER 4

Pattern of Calcification On routine radiographic testing including

standard renal tomography, calcification is seen in 7 to 18 per cent of renal cell cancers, while calcification occurs in approximately 3 per cent of cysts (Table I). Cannon, Zanon, and Karras in 196Or’ presented 6 cases of calcification in cysts, with the finding of malignancy in 5 of these cases, and ShockmanlB reported on 2 cases of malignancy in four calcified cystic masses.

In a series of renal cell tumors, Phillips, Chin, and Palubinskas5 reported that the pat- tern of calcification was more commonly stip- pled as opposed to curvilinear or peripheral. In 1966, however, Simpsonrg demonstrated curvi- linear calcification in 5 cases of renal carcinoma and Kikkawa and Lassereo reported that in 9 of 11 cases of renal cell carcinoma the form of calcification was “ring-” or “rim-like.” In a clas- sic article, 111 calcified renal masses were classi- fied by Daniel et a1.4 They concluded that, in cases of nonperipheral calcification within a mass, the chances of malignancy were over- whelming: 87 to 95 per cent. Only 2 per cent of cysts were calcified, but of these calcified cysts, 20 per cent were associated with malignancy Therefore, location of calcification was be- lieved to be of primary predictive value in this series. Other studi&1-23 disputed this finding, demonstrating that location of calcification could not predict the pathologic entity.

353

TABLE I. Calcified renal masses

Source

Daniel et ~1.~

No. of No. of Renal Pattern of -Renal Masses- Cell Carcinoma -No. of Cysts- Renal Mass

Calcified Calcified Calcified Calcification in Total (%I Total (%) Total (%I Documented Cancers

2,709 111 (4.1) 560 58 (10.3)

Phillips et ~1.5 225 26 (11.5)

Kikkawa and LasserzO 111 12 (11.0)

Krieger et ~1.~~ Sniderman et al25 > ’ ’ . .

Braasch and Griffen2 . . * .

Cahill and Melicow3

Watson et aLz4 1 1 1 1 Ochsner et ~1.~~ . . . . Shivers and

Axilrod32 . . . . Gilles33 . . * . Austen34 . . . . Hepler35 . . . .

66 9 (14.0)

1,946 39 (2.3) 54 nonperipheral 4 peripheral

89 3 (3.0) 8 nonperipheral 1 peripheral

60 11 (18.0)

231 18 (8.0)

283 7 (2.5) . . * .

82 12 (14.0) 100 3 (3.0) 103 7 (7.0)

(15.0) ‘34 13 (38.0) 85 14 (16.0) . . . .

1 (2.0) 2 nonperipheral 11 peripheral

. . . *

. . . .

. . . .

249 9 (3.6)

TABLE II. Calcified renal masses (CT experience)

No. of No. of Renal Pattern of --Renal Masses- -Cell Carcinomas* -No. of Cysts- Calcification

Calcified Calcified Calcified in Renal Cell Source Total (%) Total (%I Total (%) Carcinomas

Weyman et a1.28 . . 21 . . 11 . . 8 Soft-tissue mass extending beyond Cat + (11)

Kim et aLze . . 5 * . 3 . . 1 Nonenhancing peripheral Ca+ + (2)

Cyst y!h peripheral

Yiu-Chiu et aLz2 . , 5 . .

Patterson et al. 412 13 (3%) 88

88 TOTALS 44 *Not all histologically confirmed.

4 * . 1 Soi: mas!!vith rim Ca+ + (1)

Complex mass with rim Ca+ + (1)

Irregular solid mass with mottled Ca+ + (1)

Thick-wall Ca+ + and mass (1)

4 177 4 Mass with focal Ca’ + (2) Soft-tissue mass with

Ca+ + along rim (2) 22 177

- 14

Can calcified renal masses be characterized 17 calcified renal cell carcinomas in 1979, all of more effectively with respect to malignancy which were studied angiographically. Seventy without the use of CT scanning? per cent of masses were hypo- or avascular and

Angiography has been reported to distinguish resulted in an accuracy-prediction rate of only malignancy from benign lesions in 97 per cent of 44 per cent in the diagnosis of malignancy.23*25 patients.24 Krieger and associatesz3 reported on Angiography is believed, therefore, to be most

354 UROLOGY / APRIL 1987 i VOLUME XXIX, NUMBER 4

_,. . ,. FIGURE 1. (A) Central calcification with solid mass; pathology- dit&osis: renal cell cancer. (B) Water- density mass with peripheTa1 calcification; pathology diagnosis: cyst. (C) Near water-density ma.ss with pe- ripheral calcification; pathology diagnosis: cyst.

TABLE III. Calciied renal masses on CT UKMULexington VAMC experience Other Benign Follow-up Studies

CT D, Cancer cyst Conditions Only No Confirmation Cancer: 4 3 0 0 0 1 cyst: 4 0 0 0 3* 1 Indeterminate: 2 0 2 0 0 0 Pyogenic reaction 0 0 2t l$ 0

(benign): 3 *Follow-up CT at five, seven, twenty months: no change. txanthopyelonephritis (1)) healed infarction (1). fPolycystic kidneys.

TABLE IV. Predictabilitg of malignancy using CT criteria Uniform

Soft Tissue Mass Water-density Center Extending Beyond Histologically No Detectable Histologically Histologically

Source Calcification Proved Ca Soft Tissue Mass Proved Ca Indeterminate Proved Ca

Weyman 10 9 8 0 3 2* et a1.28

UKMC 3 3 3 0 2 0

12/13 (92%) o/11 (0%) 21.5 (40 % )

*One cystadenccarcinoma; 1 adenoma.

helpful only in cases of mass enhancement on CT.2e

Ultrasonography is plagued by calcification- induced shadowing and reverberation in the differentiation between cyst and solid tu- mor.20,27 Ultrasound and CT appeared to be complementary in a presentation of 5 cases of calcified renal masses (1 benign cyst and 4 renal cell cancers) . 22

CT Scanning of Calcified Renal Masses (Table II)

In the largest series of patients with calcified renal masses evaluated by CT scanning, Wey- man et uL2* reported that soft-tissue mass ex- tending beyond the calcification was the most reliable predictor of malignancy. Masses with peripheral calcification by central attenuation of water density were correctly considered benign cysts. Three of their 21 cases constituted the real dilemma of predictability in calcified renal masses, i.e., those with peripheral calcifi-

cation and central attenuation higher than that accepted for benign cysts, and were therefore considered indeterminate. Several reports in the literature reiterate this dilemma of diagno- sis in cases of multilocular cy~ts.~*~~~

At the University of Kentucky (UKMC) and Veterans Administration Medical Center, 412 renal masses evaluated by CT scanning from 1980 and 1985 were identified. Thirteen (3%) of these masses were calcified, and 8 had con- firmed diagnoses (Tables III and IV, Fig. 1). Weyman et al. 28 identified 10 patients with a soft-tissue mass extending beyond the calcifica- tion, 9 of which constituted malignancy. When this criterion was used, CT scanning correctly identified 3 of 3 renal cell cancers at UKMC. CT scanning correctly identified benign lesions with a uniform water density center and calcifi- cation confined to the wall, with no detectable soft-tissue mass in both series. Two of 2 indeter- minate lesions in the UKMC series were con- firmed benign cysts, but Weyman et ~2. report 1

UROLOGY / APRIL 1987 i VOLUME XXIX, NUMBER 4 355

cystadenocarcinoma, 1 tubular adenoma, and another benign cyst with hemorrhage. Indeter- minate lesions therefore need surgical confir- mation or close observation with frequent follow-up CT scans.

Prognosis in calcified renal cell carcinoma has been addressed specifically since the 1930s when Braasch and Griffen2 believed it por- tended good prognoses, whereas Cahill and Melicow3 predicted a worse outcome than the outcomes for those masses that were not calci- fied. Krieger et al. 23 speculated on the large size of calcified masses at presentation with simulta- neous low pathologic stage and favorable histo- logy. They observed that the tumors are slow- growing and have an apparently indolent nature.

Conclusion

In the pre-CT era, radiographic calcification was reported in 4 to 10 per cent of all renal masses. In our series of renal masses character- ized by CT scanning, only 3 per cent (13188) contained calcification. Our review of the liter- ature and our own experience suggest that the keys to determination of benign versus malig- nant calcified renal masses on CT scan are: (1) soft-tissue mass extending beyond the calcifica- tion (92% malignant), and (2) uniform water- density center with calcification confined to the wall and no soft-tissue mass (approaching 100% benign). Indeterminate masses are those not conforming to the above criteria and consti- tute 17 per cent (5129) of calcified renal masses and were found to be malignant in 40 per cent (2/5) of cases.

Although some authors suggest observation only with follow-up CT scanning, we believe that surgical exploration should be seriously considered in indeterminate cases.

University of Kentucky Medical Center Lexington, Kentucky 40536-0084

(DR. PATTERSON)

References

1. Albrecht P: Beitriige zur klinischen und pathologischen Ana- tomie der malignen Hypernephroma, Arch Klin Chir 77: 1072 (1905).

2. Braasch WF, and Griffen M: The prognosis in renal car- cinoma, JAMA 106: 1343 (1936).

3. Cahill GF, and Melicow MM: Calcification of renal tumors and its relationship to prognosis, J Uro139: 276 (1938).

4. Daniel WW, et al: Calcified renal masses, Radiology 103: 503 (1972).

5. Phillips TL, Chin FG, and Palubinskas AJ: Calcification in renal masses, ibid 80: 786 (1963).

6. Mencini RA: Calcification in a renal mass, Sem Radio1 17: 90 (1982).

7. Finkbeiner AE, Moyad R, and Hoskins P: Ring-shaped calcification of renal masses, Urology 9: 303 (1976).

8. Tsung SH, and Lin JI: Stone-like calcification of hy- pernephroma, ibid 22: 278 (1983).

9. Garvin D, Gehring GG, and Ball TP: Calcified solitary re- nal cyst in childhood, J Urol 116: 644 (1976).

10. Gellman AC, Sporer A, and Sebode J: Carcinoma of the kidney, Urology 2: 556 (1973).

11. Pozo JL: Calcified cystic adenocarcinoma of the kidney, J Roy Sot Med 74: 920 (1981).

12. Bejjani B, Faddoul A, and Edson M: Calcification and bone-marrow formation in ureteropelvic junction obstruction, Urology 20: 432 (1982).

13. McLaughlin AP, Talner LB, McCullough DL, and Leopold GR: Avascular primary renal cell carcinoma: varied pathologic and angiographic features, J Urol 111: 587 (1974).

14. Harrel JE, Reeder MM, and McAllister HA: Case of the month from the AFIP An exercise in radiologic, pathologic corre- lation, Radiology 91: 1226 (1968).

15. Suslavich F, Older RA, and Hinman CG: Calcified renal carcinoma in a patient with tuberous sclerosis, AJR 133: 524 (1979).

16. Biggers R, and Stewart J: Primary renal osteosarcoma, Urology 13: 674 (1979).

17. Cannon AH, Zanon B, and Karras BG: Cystic calcification in the kidney, AJR 84: 837 (1960).

18. Shockman AT: The significance of ring-shaped renal calci- fication, J Urol 101: 438 (1969).

19. Simpson W: Curvilinear calcification in renal carcinoma, Br J Urol 38: 129 (1966).

20. Kikkawa K. and Lasser EC: Ring-like or rim-like calcifica- tion in renal cell carcinoma, AJR 107:?37 (1969).

21. Babaian RJ, Lucey DT, and Fried FA: Significance and evaluation of calcifications associated with renal masses, Urology 12: 108 (1978).

22. Yiu-Chiu V, Chow KC, Chiu LC, and Agrawal SK: Com- puted tomography and ultrasonography in the diagnosis of calci- fied renal masses, J Comput Assist Tomogr 5: 51 (1981).

23. Krieger JN, Sniderman KW, Seligson GR, and SOS TA: Calcified renal cell carcinoma: a clinical, radiographical, and pathologic study, J Urol 121: 575 (1979).

24. Watson RC, Fleming RJ, and Evans JA: Arteriography in the diagnosis of renal carcinoma, Radiology 91: 888 (1968).

25. Sniderman KW, Krieger JN, Seligson GR, and Sos TA: The radiologic and clinical aspects of calcified hypernephroma, ibid 131: 31 (1979).

26. Kim WS, et ol: Computed tomography in calcified renal masses, J Comput Assist Tomogr 5: 855 (1981).

27. Elyaderani MK, and Gabriele OF: Comparison of various methods of diagnosis of renal cystic masses, South Med J 76: 341 (1983).

28. Weyman PI, McClennan RL, Lee JKT, and Stanley RJ: CT of calcified renal-masses, AJR 138: 1095 (1982).

29. Brown RC. Cornell SH. and Cult DA: Multilocular renal I

cyst with diffuse calcification simulating renal-cell carcinoma, Radiology 95: 411 (1970).

30. Banner MC, Pollack HM, Chatten J, and Witzelben C: Multilocular renal cysts, AJR 136: 239 (1981).

31. Ochsner MG, Brannan W, Pond HS, and Gooder EH: Re- nal cell carcinoma: review of 26 years of experience with the Och- sner Clinic, J Urol 110: 643 (1973).

32. Shivers CH, and Axilrod HD: Clinical comparison be- tween solitary cysts and malignant lesions of renal parenchyma, ibid 79: 363 (1958).

33. Gilles CL: Malignant tumors of the kidney in adults, Am J Roentgen01 Rad Ther 43: 629 (1940).

34. Austen G Jr: Calcification of renal tumors, iMd 49: 580 (1943).

35. Hepler AB: Solitary cysts of the kidney, Surg Gynecol Ob- stet 50: 668 (1929).

356 UROLOGY i APRIL 1987 i VOLUME XXIX, NUMBER 4