Electron microscopy in the diagnosis of malignant fibrous histiocytoma of the lung presenting as metastasis to the maxillary gingiva

Abstract

A rare case of an initial presentation of a metastatic lesion on the gingiva, arising from malignant fibrous histiocytoma (MFH) of the lung is reported. The role of electron microscopy in the diagnosis of soft tissue sarcomas has been studied. The ultrastructural details of a MFH are described and illustrated. The patient died within 9 weeks of the initial presentation with a gingival mass as is normal in these cases. He developed metastatic disease of the liver, lymph nodes, and bone. The role of electron microscopy in the diagnosis of soft tissue sarcomas is discussed.

Malignant fibrous histiocytoma (MFH) is one of the commoner soft tissue sarcomas in adults. The common sites of occurrence are the limbs followed by the retroperitoneum. Reports of a gingival mass as the starting point for widely metastasised MFH of the lung are uncommon. Primary MFH of the lung should be distinguished from spindle cell carcinoma and inflammatory pseudotumours. This can be difficult histologically even when combined with immunohistochemistry, and may require a study of the ultrastructure. The authors present a case where the initial presentation of MFH, metastatic from the lung, was with a gingival mass. Histological examination and immunohistochemistry were interpreted variously in two opinions. Electron microscopy confirmed the diagnosis.

Case report

A 47-year-old Filipino male presented with a 6-day history of a swelling on the gingiva, on the labial aspect of the upper right incisor. He was otherwise asymptomatic. A non-smoker and an occasional social drinker, he had no history of recent dental extraction. He had undergone a complete medical assessment a year earlier as part of a pre-employment check up, and this (inclusive of a plain chest film) was normal.

The lesion was overhanging the upper right lateral incisor and the canine; it was soft, non-tender, mobile on its base, and did not bleed on touch. On careful examination, there were no palpable lymph nodes in the face and in the neck, from levels I to V. The orthopantomogram was normal. A provisional diagnosis of a granuloma pyogenicum or a fibroma was considered on clinical grounds.

An excisional biopsy was carried out under local anaesthesia. The initial histopathology report on this specimen was MFH. This was based on light microscopic assessment and immunohistochemistry where alpha-1 antitrypsin, lysosome, vimentin, and Leucocyte Common Antigen were positive, and desmin, S100, cytokeratin, and Carcinoembryonic Antigen were negative. A repeat of the clinical examination 2 weeks after presentation revealed a hard, locally infiltrating right supraclavicular lymph node, about 1.5 cm × 1 cm; this was absent during the initial examination. Fine needle aspiration done on the same day on the lymph node was reported as metastatic from a MFH.

A plain film of the chest was taken, and revealed a mass lesion in the right upper and mid-zones. Computed tomography (CT) scans of the thorax revealed a rounded mass lesion in the right apex. This extended to the hilum and contained areas of necrosis. Mediastinal lymph nodes were seen in the precarinal and aortic region.

A second opinion from a larger facility was large cell carcinoma of the lung.

Bronchoscopy showed complete occlusion of the right apical bronchus with narrowing of the anterior and posterior bronchi of the upper lobe. The biopsy done endobronchially did not contribute to the diagnosis.

CT scans of the liver revealed a likely secondary (hypodense lesion) in the right lobe. A bone scan using technicium 99 MDP revealed metastasis (hot spots) in T8 and T9 vertebrae, and suspicious areas at the L5, S1 region near the left iliac crest.

The patient was treated for large cell carcinoma of the lung, using chemotherapy. Two cycles of paclitaxel and carboplatin were used. The initial response was good, but he developed parasthesia of both lower limbs, and was given palliative radiotherapy to the spinal deposits discovered by a magnetic resonance image of the spine. These symptoms subsided.

A week after the second cycle of chemotherapy, he developed acute onset of breathlessness. After a pulmonary embolism was excluded (normal pulmonary ventilation, perfusion scan), he was treated for neutropenic sepsis, but deteriorated and died the next day. The period between presentation and death was 9 weeks.

The authors sent the gingival tissue for electron microscopic analysis, as the final diagnosis remained elusive with differing opinions on the histology and immunohistochemistry. Electron microscopy revealed numerous fibrocystic giant cells with multiple nuclear profiles. The nuclei showed prominent nucleoli and a thin rim of heterochromatin. The cytoplasm showed abundant rough endoplasmic reticulum with dilated cisterns. Fine cytoplasmic filaments were sometimes seen ( Figs. 1 and 2 ).

Fig. 1
Electron microscopy showing fibrocystic giant cells with multiple nuclear profiles. The nucleolus is prominent (arrow). Dilated endoplasmic reticulum (arrowhead) and fine filaments (asterisk) are seen in the cytoplasm. Magnification 2700×.

Fig. 2
Electron microscopy showing fibrocystic giant cells with multiple nuclear profiles. The nucleolus is prominent (arrow). Dilated endoplasmic reticulum (arrowhead) and fine filaments (asterisk) are seen in the cytoplasm. Magnification 4200×.

Other malignant cells exhibited condensed chromatin in the nucleus and membrane bound lysosomal granules in the cytoplasm ( Fig. 3 ). An occasional spindle fibroblastic cell with pyknotic nucleus and abundant dilated rough endoplasmic reticulum was also seen ( Fig. 4 ). There were no desmosomes, tonofilaments, and thin actin-like filaments, microvilli, keratohyalin granules or basement lamellae around the cells.

Jan 24, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Electron microscopy in the diagnosis of malignant fibrous histiocytoma of the lung presenting as metastasis to the maxillary gingiva
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