Besides of prostatic adenocarcinoma, there are a few other types of neoplasms occurring in prostate which are difficult to determine their primary origins, such as prostatic squamous carcinoma . Lymphomas of prostate, either primary or secondary, are very rare. The types are mainly consisted of B-cell lymphomas , including diffuse large B-cell non-Hodgkin’s lymphoma (DLBL) , mucosa-associated lymphoid tissue (MALT) lymphoma , and mantle cell lymphomas . Only three cases of T-cell lymphomas involving the prostate have been reported, but none of them was primary [10, 11]. According to the criteria of Bostwick , primary prostatic lymphoma could be diagnosed subject to the fulfillment of the following conditions: primary symptoms are attributed to prostatic enlargement; the disease is almost localized to the prostate; and, NKTCL diagnosis does not include lymph nodes, liver, spleen and other organs in 1-month. The symptoms of the present case were only associated with prostatic hyperplasia, and no tumor was detected in other organs through the systemic PET-CT detection. In this manner, the primary lymphoma of prostate was confirmed. The tumor showed typical angiocentric and angiodestructive growth patten, a typical immunophenotype expressing CD56, CD3ϵand EBERs positive detection with ISH. Collectively, the lesion was best recognized as NKTCL.
Cell morphology of NKTCL is comprehensive. Most cases comprise middle cells mixed a few small- and large-sized cells, and usually do not have nucleoli. The present case is mainly composed of large or anaplastic cells containing several nucleoli. This tissue change may indicate a poor prognosis . Expression of CD30, an important marker for anaplastic large-cell lymphomas, in NKTCL is rare. One case of CD30+ NKTCL occurring on skin was reported in 2008 . In that case, Strong CD30, CD3ϵand CD56 immunoreactivities were noted in large atypical mononuclear cells. That patient died within 8 months after the onset of skin lesions. In another report, fine-needle aspiration of an large adrenal mass and CSF cytology showed that large atypical cells were positive for CD30, CD43, and CD56. The patient also died a few days after the final diagnosis was achieved though with high dose intravenous dexamethasone . The case in the present study also revealed diffusely CD30 expression in large tumor cells. According to these cases, it is speculated that NKTCL with large cells can express CD30 and indicate a worse prognosis. But more cases are necessary to prove it. In 2013, 17/40 cases CD30-positive were found in a report of 73 cases at MD Anderson cancer center, but had no further discussion about clinical threatment and prognosis .
The rearrangement TCR genes is an important supplement to the diagnosis of T-cell non-Hodgkin lymphoma. TCR genes are clonally rearranged in most cases of PTCL, NOS , while only a small proportion of NKTCLs show clonal rearrangement [16, 17]. However, some studies identified monoclonal TCRG gene rearrangement in a significantly higher proportion of NKTCLs, suggesting a mixed NK/T-cell differentiation in a subset of these tumors [18, 19]. The present case maybe belong in this subset.
Though with characteristic microscopic finds and Immunohistochemical expression, differential diagnosis is requisite before making a definite NKTCL, since prostatic NKTCL is so rare. Poorly differentiated carcinoma with diffuse tumor cells might represent some histological similarity with NKTCL, but it usually dose not display angiocentric distribution with large geographic necroses and lymphoepithelial lesions, and it often can be found some heteromorphic glands. Immunohistochemical results show expression of epithelial markers such as CK, CK8/18 and PSA et al., rather than lymphocyte ones. Another rare tumor, prostatic stromal sarcoma, is often showed pervasive small and medium-sized round cells around the residual glands too . It is suspiciously derived from mesenchymal pluripotent stem cells in the prostatic stroma and usually express CD10, CD34 and PR.