Acanthosis nigricans is a skin condition characterized by velvety, darkened patches on the skin. While this condition can sometimes be linked to benign factors like obesity or insulin resistance, “malignant acanthosis nigricans” is associated with an underlying internal cancer. Recognizing this form is important, as it can indicate a serious health issue.
Understanding the Skin Changes
Malignant acanthosis nigricans causes distinct skin changes. Affected areas appear hyperpigmented (dark brown to black) and have a thickened, velvety texture. These lesions commonly appear in skin folds like the neck, armpits, and groin.
The onset of these skin changes can be sudden and widespread, often covering extensive areas. Unlike benign forms, malignant acanthosis nigricans may involve unusual locations like the face, elbows, knees, and even mucosal surfaces such as the mouth, nose, larynx, or esophagus. Rapid progression helps distinguish them from other types of acanthosis nigricans.
Connection to Internal Malignancies
Malignant acanthosis nigricans is a paraneoplastic syndrome, a distant effect of underlying cancer not caused by tumor invasion. It can appear before, during, or after cancer diagnosis.
Most linked malignancies are adenocarcinomas, especially gastrointestinal. Gastric adenocarcinoma (stomach cancer) is the most common, accounting for 55-69% of cases. Other associated cancers include lung, breast, ovary, pancreas, liver, and prostate.
The exact mechanisms are not fully defined, but involve tumor-produced substances. Tumor cells may release growth factors like transforming growth factor-alpha (TGF-α), epidermal growth factor (EGF), and insulin-like growth factor-1 (IGF-1). These stimulate skin cell (keratinocytes and fibroblasts) and melanocyte proliferation, causing thickening and darkening.
Identifying the Underlying Cause
When malignant acanthosis nigricans is suspected, the diagnostic process focuses on identifying the underlying internal malignancy. A thorough physical examination and a detailed medical history are the initial steps to gather information about the patient’s symptoms and overall health. The presence of rapidly developing, extensive skin lesions, especially in unusual locations, or associated symptoms like unexplained weight loss, raises strong suspicion.
Investigations often include blood tests to check for general health markers and tumor markers, which can provide clues about potential cancer. Imaging studies, such as computed tomography (CT) scans or magnetic resonance imaging (MRI), are commonly used to visualize internal organs and detect tumors. Depending on the suspected cancer type, endoscopy or colonoscopy may be performed to examine the gastrointestinal tract directly. A skin biopsy can confirm the diagnosis of acanthosis nigricans and help rule out other skin conditions, though it does not specifically distinguish between benign and malignant forms.
Treatment and Outlook
The primary approach to treating malignant acanthosis nigricans involves addressing the underlying cancer. Successful treatment of the malignancy, such as through surgery, chemotherapy, or radiation, often leads to the resolution or significant improvement of the skin lesions. The skin changes may regress as the tumor is effectively managed.
The prognosis for individuals with malignant acanthosis nigricans is closely tied to the prognosis of the associated cancer. While symptomatic relief for the skin lesions can be provided using topical treatments like emollients or retinoids, these do not treat the root cause of the condition. Cyproheptadine has shown some success in aiding the regression of malignancy-associated acanthosis nigricans by potentially inhibiting tumor-produced factors.