Brief Answer:
Please give details and post photographs.

Detailed Answer:
Hi.
Thanks for your query.
Noted your history about your wife recovering from stage 4 lung cancer. Found a little black mark with streak line at the right big toe underneath the nail. Concerned about whether this is a skin cancer.

I would like to have more details please:
- Since when is this noticed?
- Was there any trauma to the toe before noticing this?
- Please see if there is any lymph node enlargement at the groin/inguinal region?

Please post clear pictures so that I can have visual impression.
The advised modality in such a case are:
- Dermatologist's or OncoSurgeon's opinion.
- Trephined biopsy of the black mark and hydrogen peroxide test as it will dissolve the hematoma but not the cancer cells.
- This is basically to be differentiated from the hematoma which appears almost same.

Please give the feedback and post the photograph.

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Brief Answer:
Looks suspicious. Thanks for clear pictures.

Detailed Answer:
Thanks for the pictures.
Such a single spot without obvious injury is definitely a suspicious lesion.

I would advise the following in such a situation as discussed above:
- Dermatologist's or OncoSurgeon's opinion.
- Trephined biopsy of the black mark. In this a drill or a punch is used to remove the small part of the nail above the lesion so that the part of the tissue can be removed and sent for histopathology examination.
- This be done ASAP.

I hope this answers your query and helps in early and proper diagnosis.
Clinical examination by an expert is also equally important.

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