Prostate Mass in an Adult

Specimen Type:

Prostate

History:

A 58-year-old man who has a normal PSA and a large irregular firm mass in the anterior portion of the prostate underwent needle biopsies.

Pathologic Features:

The biopsies show nests and anatomasing trabeculae of cells infiltrating the fibromuscular stroma (Fig. 1, 2). A sinusoid vascular network between the tumor cells is seen in some areas (Fig. 3). The cells are generally small though a mild degree of cytologic atypia such as nuclear hyperchromasia and enlarged nucleoli is seen focally (Fig 4). The tumor cells have moderate basophilic or eosinophilic cytoplasm. Mitotic figures and necrosis are absent. The tumor is negative for PSA, 34BE12, and pan-keratin, and diffusely positive for chromogranin (Fig 5) and synaptophysin (Fig 6); scattered cells show nuclear positivity for S100 (Fig 7).

Differential Diagnosis:

  • High-grade prostatic adenocarcinoma (Fig 8)
  • Invasive urothelial carcinoma (Fig 9)
  • Paraganglioma

High-grade prostatic adenocarcinoma: The high-grade tumor (Gleason pattern 4 and 5) consists of sheets and nests of acini without lumen formation. Tumor cells usually have marked cytologic atypia, including nuclear enlargement, nuclear hyperchromasia and prominent nucleoli. Basal cells are absent evident by immunostain for 34BE12, and PSA is positive in tumor cells. Neuroendocrine differentiation may be present in variable extent.

Invasive urothelial carcinoma: Urothelial carcinoma can be prostate primary or may represent direct extension of tumor arising in the bladder or urethra. Invasive cancer tends to be high grade and consists of nests of cells with marked cytologic abnormalities. The tumor cells are large, polygonal, with prominently enlarged nuclei and nucleoli, and nuclear hyperchromasia and pleomorphism. The tumor is positive for high molecular weight cytokeratin, CK7, and CK20.

Diagnosis:

Paraganglioma in the prostate

Key Features:

  • Histologically, tumor cells are arranged in nests separated by a prominent sinusoidal vascular network. The tumor cells shows clear, eosinophilic or basophilic cytoplasm; flattened sustentacular cells can be appreciated around the cell nests
  • Cytologically, nuclear atypia can be present, but mitotic figures are usually infrequent
  • Immunoprofile: cytokeratin-negative, neuroendocrine markers-positive (chromogranin, synaptophysin, and others); S-100-positive in sustentacular cells

Comment: Paraganglioma of the prostate is extremely rare, and less than 10 cases have been reported (1 child and 9 adults) (Ref. 1). Histologically, it is identical to its counterpart occurring elsewhere. In the prostate, it can be potentially misdiagnosed as high grade prostate cancer. Although the presence of prominent vascualar network between tumor cells provides a clue to the diagnosis, this feature may not be obvious throughout tumor as seen in some areas in this case. Other clinical information, such as palpable mass with normal serum PSA, is another clue. Bearing this rare tumor in mind will prompt a further investigation into the nature of tumors with similar features. With the aid of a panel of immunohistochemical markers, this tumor can be easily separated from prostate cancer. Paraganglioma arising in the bladder, urethra (Ref. 2), or pelvic soft tissue, should be excluded clinically.

References:

  1. Li QK, MacLennan GT. Paraganglioma of the prostate. J Urol. 2006 Jan;175(1):314.
  2. Boyle M, Gaffney EF, Thurston A. Paraganglioma of the prostatic urethra. A report of three cases and a review of the literature. Br J Urol. 1996 Mar;77 (3):445-8.