Ultrastructural study of a perineurioma with ribosome-lamella complexes

‘Sclerosing’ Perineurioma: A Tumor Variant?

We describe two examples of soft tissue perineurioma, a hard tumor, 1.7 cm in diameter, involving the dermis and superficial subcutaneous tissue of the left thumb, and the other a massive, lobulated lesion of the pelvis. Both occurred in 49-year-old men. Both were mobile and well demarcated but unencapsulated. Their cut surfaces were white and collagenous. Microscopically, each consisted of spindle-shaped or epithelioid tumor cells in a dense stroma of haphazardly oriented collagen bundles. Spindle-shaped cells were individually distributed, whereas epithelioid cells were often arranged in cords or clusters. Cytologic atypia was conspicuous in the massive tumor, but no mitotic activity was observed. Immunostains showed diffuse reactivity for vimentin, membrane pattern staining for epithelial membrane antigen and type IV collagen, as well as patchy CD34 reactivity. Stains for S-100 protein, Leu-7, smooth muscle actin, desmin, and cytokeratin were negative. Ultrastructural studies showed perineurial cell characteristics, including slender cytoplasmic processes, numerous pinocytotic vesicles, occasional tight junctions, and discontinuous surface basement membrane. Perineuriomas featuring marked stromal sclerosis often occur in the hands of young adults, as has recently been reported; the authors considered it a clinicopathologic variant. Herein we report two sclerotic perineuriomas, one a small tumor of the thumb and the other a centrally situated, massive pelvic tumor with sclerosis and degenerative cytologic atypia. We believe that exaggerated collagen deposition in perineuriomas, occasionally associated with degenerative nuclear changes, is not a manifestation of a unique, clinically relevant tumor variant but rather a manifestation of chronicity akin to that seen in “ancient schwannoma” and ‘atypical neurofibroma.’

Ribosome-lamella complex precursors in acute monocytic leukemia: a study of 6 cases

The ribosome-lamella complex (RLC) is a cylindrical structure composed of annular lamella associated particles, regarded as ribosomes, around a central core, which is best known in hairy cell leukemia. RLC has been presumed to originate from aggregating rER and ribosomes. Incomplete and maturing RLC structures have been called RLC precursors (pre-RLC). The present paper investigates the various architectural aspects of pre-RLC and the ultrastructural characteristics of the blasts in 6 cases of acute monocytic leukemia (M5) in which these structures occur. Blasts bearing pre-RLC contained irregular nuclei with less heterochromatin and a prominent nucleolus, and many cytoplasmic organelles in an abundant cytoplasm. The findings indicate that pre-RLC might result from an asymmetrical differentiation of organelles in blasts associated with expression of CD117 and CD56 but default of CD14 in M5.

Perineurioma: a clinicopathological study of eight cases

AIMS

Perineuriomas (PN) are uncommon, benign neoplasms that mimic a number of benign and malignant soft tissue lesions. There are two main forms: a rare intraneural PN (IPN), and a relatively more common extraneural soft tissue PN (STPN) including a conventional form (STPNc), sclerosing (SPN), reticular and lipomatous variants. Their diagnosis requires immunohistochemical (IHC) and/or ultrastructural (US) confirmation of perineurial cell differentiation. This study aims to review the clinicopathological features of eight PN we encountered recently, to raise awareness of PN as an entity and to highlight the differential diagnoses which include potentially aggressive lesions.

METHODS

Clinical, histological, IHC and US features of seven STPN and one IPN were studied.

RESULTS

The eight PN arose in the limbs of six females and two males aged 30-58 years. Five STPN occurred in subcutis, one intramuscularly and one intradermally. The STPN were well-circumscribed, multinodular growths. STPNc contained bland spindle cells with long cytoplasmic processes arranged in lamellae, storiform patterns and whorls. Three SPN were acrally located and additionally contained small epithelioid cells in cords and clusters in a myxohyaline stroma with extensive sclerosis. One SPN had giant collagen rosettes of spiral collagen. The IPN showed 'pseudo-onion bulbs' of perineurial cells. All PN were at least focally EMA positive, six of eight were Claudin-1 positive and all were S100 protein negative. Common US features were organelle-poor cell processes, many pinocytotic vesicles, sparse intermediate filaments, and tight junctions and patchy external lamina. There were no recurrences (follow-up 1-49 months).

CONCLUSION

PN has a variable morphology and can mimic many benign, borderline and malignant lesions, the differential diagnoses of which are discussed. When confronted with a subcutaneous (in particular) spindle and/or epithelioid cell lesion, EMA/Claudin-1 stains and/or US are essential to identify PN and thereby avoid inappropriately aggressive therapy.

Intra-osseous soft tissue perineurioma of the inferior alveolar nerve

This report describes an intra-osseous perineurioma affecting the inferior alveolar nerve, the second at this site, of a 53-year-old man. It produced a well defined, partially corticated, round radiolucency associated with resorption of the root apices of 36 and 37. Histology showed a circumscribed, partially encapsulated cellular tumour composed of bland spindle cells with undulating nuclei and indistinct cell membranes arranged in interlacing fascicles. The tumour was strongly positive for epithelial membrane antigen, collagen IV and laminin, with only scattered S100-positive cells and lack of CD34 expression. Electron microscopy showed elongated cells with continuous external laminae of basement membrane-like material, subplasmalemmal densities, desmosome-like junctions, and variable numbers of micropinocytotic vesicles. The lesion was surgically excised and in 9 months there has been no recurrence.

Extraneural retiform perineuriomas. A report of four cases

We present here four cases of extraneural perineurioma (EP), which occurred in 31, 32, 42 and 43 year old women in the left hand, right arm (2 cases) and right axillary regions, respectively. All tumors were well circumscribed, with a thin capsule. They were 2, 2, 1.5 and 1.5 cm in the largest diameter. Microscopically all tumors had a distinctive appearance composed of interconnected cords of cells which ran in a parallel fashion or formed a characteristically looking cellular lattice. These cords were composed of cells with tapered to stellate shaped nuclei having one or two inconspicuous nucleoli. The space between the cells of the lattice was edematous and empty looking, or it was composed of myxoid matrix, or it was filled with characteristically looking globular deposits of collagen extracellular matrix. These globular deposits of collagen extracellular matrix often indented the nuclei, giving them a stellar appearance. Immunohistochemically all tumors reacted positively with antibodies to epithelial membrane antigen. Antibodies to smooth muscle actin, muscle-specific actin, S-100 protein, cytokeratin AE1/AE3, cytokeratin CAM 5.2, and HMB-45 gave uniformly negative immunohistochemical results.

Perineurioma of the finger: case report of a rare peripheral nerve sheath neoplasm of pure perineurial cell lineage

A 1.9-cm extraneural soft tissue tumor located on the palmar aspect of the index finger of a 50-year-old woman was excised. Depicting many histopathologic patterns and a full range of cellularity, the tumor was exclusively composed of epithelial membrane antigen/vimentin-positive and S-100 protein/Leu-7-negative neoplastic cells of perineurial lineage. Soft tissue (extraneural) perineurioma, a rare variant of benign peripheral nerve sheath tumor, should be included in the differential diagnosis of tumor and tumor-like conditions affecting soft parts of the hand.