Fine needle aspiration cytology and cell block in the diagnosis of seminoma testis

Abstract

Testicular neoplasms which show a wide variety of morphologic types, comprise a small proportion of malignancies. Early identification and treatment is essential for achieving long term survival. The cytologic findings in fine needle aspiration smears from left testicular swelling of a 49 year old male suggestive of a germ cell tumor was complimented by cell block preparation as seminoma. This was confirmed by histopathologic studies. We are presenting this case to emphasize that cell block can be used for diagnosis of testicular tumors.

Introduction

Testicular neoplasms, which comprise a wide variety of morphologic types, constitute a small proportion of malignancies. Early identification and treatment is essential for achieving long-term survival.[1]

Needle aspiration of the testis was first described by Huhner in the initial decades of this century for investigating male infertility.[2]

Fine needle aspiration cytology (FNAC) is being increasingly used to diagnose tumors from many body sites.[3]

Its value in the diagnosis of testicular tumors is debated, with some workers advocating its routine use and others condemning the procedure.[4,5]

Seminoma, the most common testicular germ cell tumor, constitutes about 50% of all testicular germ cell tumors.[6,7] They occur at a mean age of about 40 years, approximately at a mean age that is 10 years higher than that of patients with non-seminomatous tumors.[6]

Cell block technique, or paraffin embedding of sediments of hemorrhagic aspirates or fluids, uses histologic techniques for processing and thus offers multiple sections of the same material, which may be processed for routine stains, special stains and immunocytochemistry. It also has increased rate of detection of cancer and helps in recognition of histologic patterns of disease.[8–11]

Case Report

A 49-year old man presented with a left testicular mass that had grown slowly and progressively over the last four months. The tumor was painless and otherwise asymptomatic. Physical examination revealed a diffusely and uniformly enlarged left testis with an external diameter of 5 cm. The contralateral testis was normal, and no regional lymph node enlargement was detected.

Radiological examination revealed a nodular lesion measuring 2 cm across in the left testis.

Ultrasound-guided fine needle aspiration was performed under aseptic precaution using a 10.0-mL glass syringe fitted with a 23-gauge needle. Wet-fixed and air-dried smears of the aspirates were stained by the Papanicolaou and May-Grünwald-Giemsa methods respectively. Remainder of the aspirate in the syringe was sent for cell block preparation, which was done using the fixed-sediment method (95% formalin and 5% alcohol). FNAC smears from the lesion showed discohesive large tumor cells dispersed in singles with granular cytoplasm, enlarged nucleus; and many with prominent nucleoli. The background was “tigroid” with variable amounts of lymphocytes [Figure 1]. With these features in mind, a diagnosis of germ cell tumor of testis was considered.

Figure 1.

FNAC smears show uniform, round-to-oval monotonous population of tumor cells in tigroid background (H and E, ×450)

On cell block preparations, sections studied showed sheets of monotonous population of cells. Individual cells were round with eosinophilic cytoplasm, altered nucleo-cytoplasmic ratio with prominent nucleoli [Figure 2]. Taking into consideration the findings of both FNAC and cell block, a diagnosis of seminoma was given. Tumor markers were done on cell block. Both periodic acid Schiff (PAS) stain and FF (PLAP) placental alkaline phosphatase were positive. Thus cell block corroborated the diagnosis suggested on FNAC.

Figure 2.

Cell block shows monotonous population of tumor cells with eosinophilic cytoplasm (H and E, ×450)

A left orchiectomy followed the cyto-diagnosis of seminoma, which on gross examination measured 7×5×5 cm. The cut section revealed a well-circumscribed lobulated grey-white homogenous mass measuring 5×4 cm. On microscopy, sections showed a tumor composed of cells arranged in lobules and sheets with intervening thin fibrovascular septa. The cells had moderately eosinophilic-to-clear cytoplasm, round nuclei, with some of them showing conspicuous nucleoli [Figure 3]. Scattered syncytiotrophoblastic giant cells were also seen along with mild lymphocytic infiltrate in the septa. Thus, the cyto-diagnosis was histopathologically confirmed.

Figure 3.

Section studied shows tumor cells arranged in sheets separated by thin fibrovascular septa (H and E, ×450)

Discussion

Testicular FNAC has not readily become a routine clinical method, although there are several advantages of this method over open biopsy.[12] FNAC is essentially non-traumatic and easy to carry out, but it requires considerable practice in its execution and in the interpretation of the aspirates. FNAC is believed to be the technique of choice for the study of the pathology of the scrotal content. The main advantage is avoiding delays in diagnosis. The method failed to develop into a routine investigation, possibly due to the fear of needling trauma and local tumor implantation as well as lack of information on interstitial tissue and tubular basement membrane on FNAC smears.[4,5]

For years, open biopsy has remained the method of choice in testicular investigation, but it has many disadvantages.[12] The tissue sample is often very small and not representative of the entire testis. Moreover, since the testis is a delicate tissue, the biopsy procedure causes many artefacts, resulting in problems with histologic interpretation.

In aspirates, seminoma shows primarily a dispersed cell population of large cells with scant-to-moderate cytoplasm, round-to-slightly irregular nuclei, finely granular chromatin with one or more prominent nucleoli. Variable number of lymphocytes and plasma cells are intermingled with the tumor cells, and there are a few cases with epithelioid histiocytes or the characteristic “tigroid” background. The tigroid smear background tends to be seen in hypercellular aspirates and is often not seen in less cellular samples.[13] Its presence is not considered pathognomonic of seminoma since similar findings have been seen in aspirates of melanoma, squamous cell carcinoma, renal cell carcinoma and synovial sarcoma.[14]

The key diagnostic features for the identification of seminoma are the monotonous discohesive population of large seminoma cells in a background of small, mature lymphocytes. The differential diagnosis includes other neoplasms that present with a discohesive smear pattern. These include the discohesive variant of adenocarcinoma, melanoma and lymphoma, respectively. Seminoma on cytology can be mistaken for other round cell tumors, like lymphoma of testis. However, cell block can be used to discuss the morphological details better as the treatment of seminoma and lymphoma is different. Cell block is thus known to increase the sensitivity and specificity of any diagnosis. Also various immunostains can be done on a cell block to give a more specific diagnosis and thus enable to decide the line of management.[8,9,11]

Embryonal carcinoma lacks the regular fibrous septa of seminoma. Immunopositivity for cytokeratin and CD30 stain may be used to differentiate it from seminoma.

Lymphoma cells usually lack the clear cytoplasm and well-defined cell borders that typify seminoma. Leukocyte common antigen and other lymphoid markers are usually positive in lymphomas.

Metastatic tumors, including renal cell carcinoma[14] and malignant melanoma, may create differential diagnostic difficulties with seminoma. Clinical history and immunostains like cytokeratin, HMB 45 and melan-A may easily resolve such an issue.