Rabbit monoclonal antibody (MAb), which has become available only recently, theoretically combines the advantage of the high affinity attributable to its rabbit origin and the high specificity due to its monoclonal nature. Since immunohistochemical demonstration of cyclin D1 is notoriously difficult, this study aims to assess whether a newly available rabbit MAb against cyclin D1 (SP4) can improve the consistency of immunostaining, especially for the diagnosis of mantle cell lymphoma (MCL). A total of 150 cases of lymphoproliferative lesions, including 30 cases of MCL, histologic mimickers of MCL, and various types of lymphomas and leukemias, were studied. Immunostaining was performed on formalin-fixed, paraffin-embedded tissue sections using a labeled streptavidin-biotin peroxidase system in an automated immunostainer. All cases of MCL expressed cyclin D1, with a higher median staining score (8 out of a maximum of 12) compared with mouse MAb DCS-6 (score 4). In addition, 2 of 15 cases of B-cell chronic lymphocytic leukemia (B-CLL), 3 of 12 cases of multiple myeloma, and 2 of 5 cases of hairy cell leukemia were also positive. Comparable staining results could also be achieved by an optimized manual staining protocol. This study thus confirms the superior performance of the rabbit MAb SP4, which should permit consistent immunostaining for cyclin D1 to be readily achieved. The value of cyclin D1 immunohistochemistry in the differential diagnosis of MCL from other low-grade B-cell lymphomas is also affirmed, but with the caveat that rare cases of B-CLL can also be cyclin D1 positive.

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Neurotrophic tyrosine receptor kinase ( NTRK)-rearranged spindle cell neoplasm is a recently described soft tissue tumor entity that occurs predominantly in children and young adults. The diagnosis of this tumor is difficult due to the nonspecific and highly variable morphology, yet it is of clinical relevance because of the availability of highly effective TRK inhibitors. In this article, we report the case of a 40-year-old female who presented with a mass in the left calf. Histologic examination revealed a low-grade sarcoma consisting of monomorphic spindle cells accompanied by abundant myxoid stroma, a feature that had not been emphasized in the reported cases of NTRK-rearranged tumors. The tumor cells expressed CD34 and S100 but not SOX10, and they showed positive staining for pan-TRK. Next-generation sequencing showed the presence of LMNA-NTRK1 fusion. The patient developed several episodes of lung metastases that eventually became unresectable. TRK inhibitor was given that led to near-complete resolution of the tumors.

Aims. We report on the unusual case of a 43-year-old man who developed recurrent meningeal hemangiopericytoma and presented with hypoglycemia 6 years after excision of the tumor. Methods and Results. We utilized computed tomography to assure multiple tumor metastasis and cranial recurrence of previous meningeal hemangiopericytoma and clinical laboratory tests and immunohistochemical staining to characterize this case. Magnetic resonance imaging and computed tomography showed the recurrent tumor at original torcular site was increased in size. Abnormal low levels of growth hormone, insulin, and insulin-like growth factor-I except insulin-like growth factor-II were detected in the serum. By immunohistochemistry, the neoplastic cells characteristically express diffusely CD99, bcl2, and variable CD34. After radio- and chemotherapy, serum glucose level of the patient returned to normal. Conclusions. Comparing other brain tumors, meningeal hemangiopericytoma has a higher recurrent and metastatic rate, but this tumor with hypoglycemia is very rare.

A 72-year-old man presented with a 2-year history of epiphora. CT revealed an extensive inferomedial orbital tumor connected to the lacrimal sac and duct. Incisional biopsy revealed malignant oncocytoma of the lacrimal sac. The patient was treated with exenteration and maxillectomy followed by a course of postoperative radiotherapy. Patients with malignant oncocytoma may present with simple epiphora in absence of other signs and symptoms such as blood stained tearing or purulent rhinorrhea.