Non–small cell lung cancer presenting as back cyst

Abstract

Cutaneous metastasis as the presenting sign of lung cancer is rare, with a poor prognosis and a life expectancy of 3 to 5 months. We present the complicated course of a 60-year-old woman with extensive metastatic non–small cell lung cancer that presented as a back cyst. Due to the benign appearance of the cyst and the difficulty discovering the location of the primary malignancy, diagnosis and treatment were delayed. Unfortunately, once aggressive treatment was initiated at the request of the patient, she died 2 weeks later. This case highlights the importance of recognizing cutaneous lesions as a sign of internal malignancy and emphasizes multidisciplinary discussion that focuses on the patient’s quality of life.

Recognizing the signs and symptoms of lung cancer is important for rapid diagnosis, determination of prognosis, and initiation of treatment. Although the most common presenting symptoms of lung cancer include cough, hemoptysis, chest pain, dyspnea, and weight loss, clinicians should be aware of rare presentations. This case presents a patient with a back cyst as the first sign of non–small cell lung cancer (NSCLC).

CASE PRESENTATION

A 60-year-old female smoker presented to her primary care physician with a new painful back cyst. Ultrasound showed a 2.5 cm subcutaneous mass. She was diagnosed with an infected sebaceous cyst and prescribed oral antibiotics. Despite antibiotics, the back cyst continued to grow, and her pain increased. The cyst was excised, and biopsy showed a malignant epithelial tumor with mucinous differentiation. Staging computed tomography (CT) scans of the chest discovered a cystic mass in the subcutaneous tissues, mediastinal lymphadenopathy, and a 2.2 × 1.9 cm spiculated mass in the right upper lobe of the lung (Figure 1a, 1b). By the time of her initial oncology visit, she had developed complete blindness in the left eye and was admitted to the hospital for further care.

Figure 1.

CT of the chest, (a) axial view and (b) coronal view, showing a spiculated mass in the right upper lobe with adjacent scarring and mediastinal lymphadenopathy. (c) MRI of the brain, sagittal plane, showing multiple areas of leptomeningeal enhancement. (d) Bedside soft tissue ultrasound of a malignant axillary lymph node for fine-needle aspiration.

The physical exam was pertinent for left and right anterior cervical, left submandibular, and right axillary lymphadenopathy, a tender mass under the left jaw, and unequal pupils with a constricted left pupil with no response to light. Magnetic resonance imaging (MRI) revealed multiple areas of leptomeningeal enhancement within the brain (Figure 1c), choroidal metastasis, retinal detachment, a right lung mass, mediastinal and right hilar lymphadenopathy, and widespread metastasis in the bone, muscle, and subcutaneous tissue. Ultrasound-guided fine-needle aspiration of the axillary lymph node (Figure 1d) detected poorly differentiated NSCLC. Immunohistochemical staining demonstrated diffusely positive CK7, beta-catenin, and p53. The staining was negative for lung, colon, and breast markers. Programmed death-ligand 1 (PD-L1) was 0%. Lumber puncture was positive for malignant cells, and she was diagnosed with NSCLC with extensive metastasis.

The patient opted for aggressive management; cranial irradiation was promptly initiated. Palliative care was involved with symptom management, and her medical care was transferred to a hospital closer to her home. She received one dose of intrathecal chemotherapy but died shortly after. Next-generation sequencing (NGS), resulted postmortem, found a potentially actionable KRAS mutation (p.G12C) and multiple biologically relevant mutations, including NFE2L2, STK11 p.E223, et al., most commonly reported in lung carcinomas.¹ NGS tumor origin and RNA sequencing reported lung adenocarcinoma with an 85% estimated probability.

DISCUSSION

The percentage of primary lung cancer patients who present with skin metastasis ranges from 1% to 12%.^2,3 Currently, there is not clear agreement on which lung cancer type has the highest frequency of skin metastasis. Some studies have shown that adenocarcinoma is the most common type, while others show large cell carcinoma.^4–7 A broad range of primary skin morphologies are seen in the various reported cases, ranging from a solitary nodule, exudative or ulcerated lesions, carcinoma erysipeloides, and many more.^3,8 The skin metastasis can appear after diagnosis, at the same time, or as the first sign of internal malignancy. In most cases of cutaneous metastasis from primary lung cancer, the cancer was already known.³ In a large retrospective study in which 63 lung cancer patients had skin metastasis, 75% had already been diagnosed.⁵

Cutaneous metastasis is a rare occurrence in all types of internal malignancies. Determining the location of the primary malignancy is often very difficult. In young men, melanoma is the leading cause of skin metastasis. In older men, lung cancer is more common, at 24%. In women of all ages, breast cancer is the most common primary site at 69%, with lung cancer being the least likely site at 4%.³ Once the location is determined, the treatment consists of palliative chemotherapy, radiation, or targeted therapies in patients with sensitizing mutations. Unfortunately, the appearance of skin metastasis yields a very poor prognosis, with imminent death within 3 to 5 months from the detection of the skin lesion.^5,6,9,10 Early palliative care initiation and multidisciplinary discussions on the patient’s quality of life should be the primary focus.