Late distant metastasis of adenoid cystic carcinoma to lung

Clinical History

History significant for mild dyspnoea and non-productive cough over the past several months. Distant history of adenoid cystic carcinoma (ACC) of the right lacrimal gland treated with orbital exenteration nearly two decades ago and chronic lymphocytic leukaemia. On physical examination, decreased breathing sounds and rales noted at right lung base.

Imaging Findings

Chest radiograph revealed a 2 cm solitary pulmonary nodule in the left mid-lung zone (Fig. 1). Further evaluation with CT demonstrated an irregularly shaped soft tissue mass in the superior segment of the left lower lobe without evidence of lymphadenopathy (Fig. 2). Biopsy of the lesion was performed and pathologic findings were suggestive of ACC but nondiagnostic. Wedge resection of left lower lobe was performed and showed vascular invasion from basaloid cells with a cribiform growth pattern arranged concentrically around glandlike “pseudocysts” (Fig. 3). Findings were consistent with ACC. Tumour margins were negative. He was followed with imaging until four years later when a repeat CT demonstrated a nodule suspicious for recurrent metastasis as well as pleural-based carcinomatosis (Fig. 4). Due to his history of CLL, he was precluded from experimental chemotherapy trials. Follow-up CT two years later revealed multiple bilateral lesions with worsening of pleural carcinomatosis (Fig. 5).

Discussion

Adenoid cystic carcinoma (ACC), first characterised by Billroth in 1856 and called “cylindroma” [1], is a rare neoplasm that typically arises from the salivary or lacrimal glands and compromises less than 2% of all malignant tumours of the oral and maxillofacial region [2]. Other primary sites of occurrence include the parotid, mucous glands of the nasal cavity, tracheobronchial tree, uterine cervix, Bartholin glands, and breast [2]. ACC is an invasive, slow-growing tumour composed of basaloid cells with a tendency towards perineural rather than lymphatic spread [3]. ACC demonstrates a female predominance, occurring at various ages but most commonly between the fifth and sixth decades of life [4]. Pulmonary metastases result from haematogenous spread. Direct extension into the airways may also occur along submucosal planes, and results in an intraluminal mass, similar to primary pulmonary ACC.

On imaging, primary ACC in the lung is seen intraluminally in the major airways, whereas metastatic ACC to lung is seen as solitary or multiple parenchymal nodules. Late distant metastases (most commonly to the lung) occur up to several decades after initial presentation and even after adequate locoregional control; consequently, long-term follow up imaging and clinical evaluation is recommended [5]. Distant metastases are more commonly seen in patients with a predominantly solid histologic pattern of growth as well as patients with locoregional treatment failure [6]. Bone involvement with or without lung metastases carries a worse prognosis than those with lung metastases alone [6]. Median survival ranges between 15 and 70 months after initial diagnosis of distant metastasis [6]. Many patients remain asymptomatic and functional late into the course of the disease. Prognosis is guarded for these patients given the lack of an established role for chemo or radiotherapy, although they are sometimes utilised for palliative purposes [7].

Differential Diagnosis List

Final Diagnosis

Late distant metastasis of adenoid cystic carcinoma to the lungs

URL:	https://www.eurorad.org/case/9245
DOI:	10.1594/EURORAD/CASE.9245
ISSN:	1563-4086