INTRODUCTION:Pulmonary hyalinizing granuloma (PHG) is a rare fibrosclerosing inflammatory lung disease of unknown etiology and pathogenesis, with fewer than 70 cases reported in the English-language literature. Here we describe a unique case of PHG presenting with atypical features (hemoptysis and hilar mass), ultimately diagnosed on pneumonectomy.
CASE PRESENTATION:A 39 year-old man with well-controlled hypertension and bipolar disorder presented to the local emergency department following an episode of hemoptysis in which he expectorated half a cup of bright red blood. This was preceded by the sensation of “something stuck in his throat” and associated with left-sided pleuritic chest pain. He denied any shortness of breath, fevers, cough, sputum, or fatigue. Notably, he had intermittent hoarseness and had lost 25 pounds over the previous month. He was a life-long non-smoker and worked in a cotton mill. On examination, he was comfortable and afebrile, with room air oximetry of 97%. Physical exam was unremarkable. Chest CTA revealed extensive filling defects in the left interlobar pulmonary artery, with a 2 × 3cm left hilar mass. These filling defects had an unusual, abrupt “cut-off,” and pulmonary arteriogram confirmed non-filling of the left lower lobe pulmonary artery and its branches, but with difficulty distinguishing between pulmonary embolus versus vascular encasement from the left hilar mass. MRI of the pelvis/lower extremities was negative for deep venous thrombosis. Transthoracic echocardiogram revealed mild right ventricular enlargement with normal function and no pulmonary hypertension. PET scan demonstrated an intensely hypermetabolic left hilar mass suspicious for malignancy. PPD was negative. Bronchoscopy revealed a left lower lobe endobronchial lesion with non-diagnostic pathology. All microbiology remained negative. The patient was subsequently referred for surgical evaluation. Thoracotomy demonstrated a very proximal left hilar mass, with frozen section showing dense invasive inflammatory component of lymphocytes and plasma cells. Left pneumonectomy was performed. Gross pathology showed a 4cm hilar mass completely encircling the left pulmonary artery lower lobe branch, which was filled with thrombus. Histopathology showed lamellar and branching fascicles of thick collagen with peripheral lymphocytoplasmic inflammation and scattered giant cells, without evidence of malignancy, granulomatous inflammation, or infection, consistent with pulmonary hyalinizing granuloma.
DISCUSSIONS:Pulmonary hyalinizing granuloma is a rare fibrosclerosing inflammatory lung disease of unknown etiology and pathogenesis. It is characterized histopathologically by a peripheral rim of lymphocytes and plasma cells, surrounding a central haphazard arrangement (whorled, storiform pattern) of hyalinized collagen lamellae concentrically layered around vessels, with interspersed plasma cells, lymphocytes, and giant cells. Both genders are equally affected, with reported age range of 24-77 (mean 43). 50%-75% of patients have non-specific symptoms such as shortness of breath, cough, pleuritic chest pain, fatigue, and low-grade fever. Hemoptysis is rare. Extrapulmonary fibrous lesions (oropharynx, thyroid, skin, kidney, mediastinal or retroperitoneal fibrosis) occur in 20%. Radiographically, PHG typically presents as multiple bilateral pulmonary nodules (2-4 cm) with or without calcification and cavitation. The differential diagnosis is broad, including nodular amyloidosis, rheumatoid nodules, sarcoidosis, Wegener’s granulomatosis, pulmonary chondroma, infectious chronic granulomatous diseases, inflammatory pseudotumor, nodular sclerosing lymphoma, and metastatic tumors. Potential pathogenic mechanisms include an autoimmune process and an end-stage inflammatory response to antigenic stimuli, as many patients have autoimmune phenomena or previous exposure to mycobacterial or fungal antigens. There is no effective or established treatment for PHG, and it is generally considered a benign process with good prognosis.
CONCLUSION:Pulmonary hyalinizing granuloma is a rare, non-neoplastic fibrosing disorder of the lung, usually with peripheral distribution as multiple nodular masses, but in this case presenting as central/proximal hilar fibrosis with extensive and circumferential involvement of the pulmonary artery and its lobar branches.
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