Mucinous Cystadenocarcinoma (MCA) is a rare primary tumor of the lung.
We present a case of a 64-year-old previously healthy female evaluated for 6-month history of non-productive cough. She is a life long non-smoker. Her physical exam revealed mildly decreased breath sounds over the left upper hemithorax. A chest X-Ray revealed a left upper lobe mass confirmed by a CT scan of the thorax. An attempt to make tissue diagnosis by CT guided transthoracic biopsy yielded abundant mucin with rare atypical epithelial cells. Inconclusive core biopsies and patient’s persistent symptoms required surgical resection. During surgery, significant adhesions were noticed and a left pneumonectomy was performed for complete removal. Pathologic examination revealed a well-circumscribed spherical mass measuring 8x8x6 cm in the posterior superior segment of the right upper lobe. Microscopically, there was large cysts filled with mucin and lined by an atypical columnar epithelium with areas of invasion of lung parenchyma consistent with the diagnosis of mucinous cystadenocarcinoma (MCA). Work up for a primary site other than the lung was unrevealing. The patient had a favorable post operative course and had no signs of recurrence at 6-month post resection.
Mucinous cystadenocarcinoma, a variant of adenocarcinoma, is a rare primary pulmonary tumor. MCA belongs to a group of tumors characterized by copious mucin production usually occurring in the ovary, breast, pancreas or the gastro intestinal tract. First described by Gowar in 1978, it wasn’t until 1999 that this group of tumors was divided into three different entities: Mucinous adenoma, mucinous carcinoma and mucinous cystadenocarcinoma. The exact prevalence of primary pulmonary MCA is difficult to estimate due to the confusion in classification of these tumors in the past and the inconsistencies in the terminology. When symptomatic, pulmonary MCA presents as cough, chest pain or weight loss. Radiographically, MCA appears as a benign cyst with low attenuation and characteristic enhancing septa on CT scan. Grossly MCA is a peripherally located well-demarcated tumor ranging from 1 to 13 cm in diameter. Pathologically, MCA is composed of cysts filled with copious amounts of extracellular mucus lined by a small number of columnar mucin producing neoplastic cells showing various degrees of atypia. A distinct cytopathologic feature of MCA is having invasive adenocarcinoma foci, or groups of atypical cells suspended in pools of mucin. Although MCA cytologically resembles mucinous broncho-alveolar carcinoma, the former seems to have a more favorable prognosis. Surgical resection is the treatment of choice with a favorable long-term survival. Finally, in considering the diagnosis of this rare neoplasm, the most important task for the clinician is to exclude an extrapulmonary site of origin.
Although rare in the lung, MCA should be included as part of the differential of a benign appearing lung mass. Aspiration of mucinous material by CT guided or transbronchial biopsy should further raise the suspicion for this tumor. When presenting as a pulmonary mass, an extrapulmonary site of origin should be ruled out. Surgical resection offers long-term cure.
Melhem Imad, None.