Contributed by Shaun Kian Hong Cheng, MB ChB1*, Yee Lin Tang, MBBS1*, Rao Jai Prashanth, MBBS, FRCSEd2, Khoon Leong Chuah, MBBS, FRCPA1
1Department of Pathology, Tan Tock Seng Hospital, Singapore, 2Department of Neurosurgery, National Neuroscience Institute (TTSH Campus), Singapore
A 64 year old male Chinese patient presented with generalized tonic-clonic seizures for a month prior to admission. He had a past history of diabetes, hypertension and previous cerebrovascular accident. Otherwise, he had no other constitutional symptoms such as fever, chills, weight loss etc. Physical examination did not disclose any systemic lymphadenopathy. Subsequent MRI revealed right frontal extra-axial mass with features suggestive of a meningioma which was associated with compression of the anterior portion of the superior sagittal sinus (Fig. 1a). He underwent a craniotomy and tumor excision. During surgery, an avascular right frontal enplaque tumor associated with poor brain-tumor interface was noted. A biopsy of the mass was submitted for frozen section intra-operative consultation during which smears as well as frozen tissue sections were prepared. Following the frozen section result, a subtotal resection was undertaken with residual tumor remaining in the patient.
Grossly, during intra-operative frozen section consultation, 2 pieces of tissue measuring 1.3 cm and 1 cm in largest dimension were received. The subtotal resection specimen comprised multiple pieces of tissue measuring 7x3x1 cm was submitted to the laboratory. The smears performed intra-operatively were cellular comprising predominantly lymphocytes and plasma cells associated with histiocytes. Significantly, some histiocytes displayed a characteristic feature as shown in Fig. 1b which was diagnostically helpful. The frozen tissue sections revealed an inflammatory mass (Fig. 1c) with areas of fibrosis; however the feature as depicted in Fig. 2 on the smears was not evident. Paraffin sections of the frozen section tissue and additional tissue revealed an inflammatory mass composed of lymphocytes, plasma cells and histiocytes (Fig. 1d) extending from the dura to the leptomeninges, replicating the features seen in the smear and frozen tissue sections. Marked fibrosis was present in some areas. Interestingly, there were histiocytes containing inflammatory cells within the cytoplasm as seen in the smears (Fig. 1e). The histiocytes were positive for CD163 and S-100 (Fig. 1f) but not for CD1a. What is your diagnosis?