Case of The Month
By Dr Anila R. Sharma
- 70 year-old-male presented with a huge retroperitoneal mass measuring 13 x 8 cm.
- FNAC of the mass yielded cellular smears.
- Smears were predominantly composed of cohesive sheets, papillae and tissue micro fragments of neoplastic cuboidal cells with oval regular nuclei with conspicuous nucleoli and moderate amount of cytoplasm.
DIAGNOSIS ON FNAC ????
- A solid cellular tumor displayed predominantly papillary pattern and focal tubular architecture. The papillae/tubules were lined by cuboidal /columnar cells with oval hyperchromatic nuclei with prominent nucleoli and moderate amount of clear or pale pink cytoplasm.
- Papillary renal cell carcinoma.
- Metastatic papillary adenocarcinoma.
- Germ cell tumor.
(?yolk sac tumor, ??embryonal carcinoma)
- Tumor cells expressed SALL 4,PLAP ,CD117 and PODOPLANIN ( D2-40 ) while were negative for CD30, CK, EMA and GLYPICAN-3
- Malignant germ cell tumors predominantly arise from the gonads, however 2-5% arise at extragonadal sites. They typically arise at or near the midline presenting as mediastinal, spinal or retroperitoneal masses. These extragonadal germ cell tumors (EGCTs) share same histomorphological pattern and similar serological features as their gonadal counterparts.
- 30-40% of EGCT’s are seminomas, with retroperitoneum being the favoured site after mediastinum. The existence of extratesticular seminoma has been challenged as a small occult testicular focus may be the source of a large distant metastatic mass. Abell etal (1965) developed criteria for retroperitoneal seminoma “as a retroperitoneal neoplasm that fulfills the histopathologic requirement of the seminoma and presents in the absence of detectable tumor in the testes or the subsequent appearance of such”.
- Seminoma of classical type is characterized by large tumor cells compartmentalized into small groups by a delicate fibrovascular stroma that is infiltrated by mature lymphocytes. Other morphologic variants may be in the form of tubular, microcystic or cribriform patterns, which are focal & present in conjunction with the classical pattern. When these pattern dominate the histology, they may pose a diagnostic challenge. A seminoma with tubular structures may be misinterpreted as other neoplasms like metastatic adenocarcinoma, yolk sac tumor, or embryonal carcinoma, more so in a needle biopsy, where sampling is limited.
In a tubular seminoma the neoplastic cells are arranged in varisized tubules, with focal papillae. The cells are cuboidal/columnar with abundant clear cytoplasm having large regular nuclei with characteristic nucleoli vis-à-vis the nuclei of embryonal carcinoma which are pleomorphic, irregular & show greater degree of nuclear crowding. The intracytoplasmic & extracytoplasmic hyaline inclusion seen in yolk sac tumor are lacking in a seminoma. To rule out the possibility of Metastatic adenocarcinoma IHC is prudent.
A judicious use of a panel of IHC stains may help in resolving this diagnostic dilemma. SALL4 and PLAP positivity along with EMA negativity confirms the tumor of germ cell origin and rules out epithelial origin (metastatic adenocarcinoma). CK negativity or scant focal positivity rules out YST and embryonal carcinoma as they are diffusely positive.CD117, CD30, Podoplanin, AFP, Oct 4 may be useful in distinguishing seminoma from other germ cell tumors as was in our case.
To conclude distinction of a tubular seminoma from other neoplasms is fundamental to treatment decisions. While radiotherapy is used for smaller lesions, larger lesions warrants platinum based chemotherapy.